Histochemistry, phenolic content, antioxidant, and anti-diabetic activities of Vernonia amygdalina leaf extract

Vernonia amygdalina leaves were investigated for their histochemical properties and antidiabetic activities. Histochemical analysis of the leaf revealed distributions of acidic lipid, mucilage, and pectin, lipids, polyphenols, and alkaloids at the mid rib, glandular trichome, and epidermis. HPLC analysis of the leaves hot water infusion revealed the presence of quercetin and (-)-epi-catechin. The infusion had significant (p < 0.05) 2,2′-diphenyl-1-picrylhydrazyl scavenging activity and ferric reducing antioxidant power. Ex vivo antioxidative analysis revealed the ability of the infusion to increase glutathione level, superoxide dismutase, and catalase activities, while concomitantly depleting malondialdehyde level and DNA fragmentation in Fe ²⁺ -induced hepatic injury. The infusion showed significant (p < 0.05) inhibitory activity against α-glucosidase and pancreatic lipase. It also inhibited intestinal glucose absorption and enhanced muscle glucose uptake, respectively. The ability of the infusion to abate oxidative stress, DNA fragmentation and stimulate muscle glucose uptake may suggest the antioxidative, anti-apoptotic, and insulin-sensitizing activity of V. amygdalina. Practical applications: Vernonia amygdalina (bitter leaf) is among the common leafy vegetables in West Africa reported for its various medicinal and nutritional properties. It is utilized as a food ingredient as well as supplement for the treatment and management of type 2 diabetes (T2D). Its ability to inhibit intestinal glucose absorption, enhance muscle glucose uptake, and protect against hepatic oxidative stress gives more credence to its reported antidiabetic properties. Being a common leafy vegetable, V. amygdalina can be a cheap source of nutraceutical for the treatment and management of T2D and its complications.